Permeability of cochlear partition to potassium and sodium ions

Abstract

Permeabilities of guinea pig cochlear partitions were determined by perfusing scala vestibuli (SV) and/or scala tympani (ST) with artificial perilymph with or without Na22 and K42 tracers. All concentrations of tracers were measured by gamma ray spectrometry. Perfusions ranged from 5 to 60 min at a rate of 2 μl/min. Under these conditions stimulus-related responses and endocochlear potential were not greatly suppressed. Perfusions were performed under the following conditions: perfusion of both SV and ST with tracers, perfusion of SV with tracers and ST without tracers, and perfusion of SV without tracers and ST with tracers. Results were similar under all the above conditions with concentration of K42 in endolymph becoming greater than in perilymph after 5 min of perfusion and becoming five times greater after 30 min of perfusion. On the other hand Na22 concentration is endolymph was less than 2% of that in perilymph for all perfusion times. Perfusion of SV and ST with 10−4 M ouabain or under anoxia resulted in a decrease of K42 and an increase of Na22 concentration in endolymph. These findings suggest that active transport of K into endolymph is through stria vascularis.